Decades ago in grad school, I was under my 1969 VW bus doing maintenance. Had a set of combination wrenches at curbside. Ten year old blind kid who lived next door came out and wanted to know in detail what I was doing, and I talked him through what I was doing to get ready to pull the engine to install a new clutch plate & throwout bearing.

I could see the nuts and bolts, and knew what wrench size I needed, but when I'd reach for it, I'd often pick the wrong one (13mm felt pretty much like 12mm, etc.). He asked me to say (only once) the wrench size each time I picked one off the curb. Thereafter, he told me what size I was about to select as soon as I touched it, making it scrape ever so slightly against the concrete. Saved me some time by telling me when I was about to pick up the wrong wrench.

I wasn't surprised, as I'd seen him on his bike in the neighborhood, doing the click echolocation described in This American Life. I was in a neurophysiology program at the time, and was totally impressed with his living demo of neuroplasticity and audio world mapping.